, Boeing completed a software update for the 737 Max and vowed to have the planes re-certified by the Federal Aviation Administration. Still, it remains unclear when the planes will be back in the sky.

Speaking at the 2019 Code Conference in Arizona on Tuesday, the CEO of America's second-largest airline said the incidents were "unthinkable," but defended Boeing's overall safety record and legacy.

Delta CEO Ed Bastian said on Tuesday that the airline industry is still "traumatized" by the controversy surrounding the Boeing 737 Max aircraft after a spate of deadly accidents.

Boeing has come under pressure in recent months, following two fatal crashes involving the 737 Max that killed nearly 350 people. The aircraft has been grounded by airlines around the world since March, and a malfunctioning sensor specific to the Max planes has been linked to the disasters.

Last month , the company completed a software update for the embattled aircraft and vowed to have the 737 Max re-certified by the Federal Aviation Administration. One of the largest buyers of the 737 Max plane, SpiceJet, reportedly said that Boeing assured its crisis-hit aircraft would be back in the skies by July, but no official deadline has been set by Boeing or the FAA.

Speaking at the 2019 Code Conference in Arizona on Tuesday, attended by Business Insider, the CEO of America's second-largest airline addressed the Boeing controversy and said it had left a major mark on the aviation industry as a whole.

But several airlines, including American Airlines and United Airlines , have recently jumped to Boeing's defense and have vowed to fly the 737 Max planes once they've been re-certified.

"This was truly a 'one-off' in my opinion," Bastian said of the controversy surrounding Boeing. "There's certainly going to be lessons learned and we don't know all the facts yet."

"Boeing will figure it out, I have no doubt about that," he continued. "They're a great technology company, we wouldn't be here in this room together if it wasn't for Boeing. It's fundamental to who we are, it's the lifeblood to our industry, it's not something that I'm concerned about."

When asked if Delta has "second guessed" its relationship with Boeing in the wake of the accidents, Bastian stood firm that business would remain unchanged.

"60% of the airplanes we fly are Boeing," he said. "Boeing has been the most successful aviation company in the world."